My WR died today

[Nathanael]

It died in the air while on a track. I nearly ate it hard.

But the question here is why did it happen? To continue further the bike would not start at all after it happened.

I have a theory, tell me what you think.

First, to start, my bike is a 2002 WR426.

In wanting auto-decompression I had posted a few times on here trying to find the best solution. It was determined that the Hot Cams would likely be the best solution, but I wasn't able to afford them both. Since the exhaust cam was the only one I needed for auto-decompression I was just going to get that hot cam when it was suggested that I get the OEM 03 YZ Exhaust Cam.

I did just that, and installed it exactly one week ago.

When doing so, I compared the new cam to the old one and noticed that the teeth were just slightly different. I read up on it online and confirmed that was what I should find and that I shouldn't worry, all would be okay.

I finished the install and took it out for a good desert ride on Labor Day, doing around 50 or so miles. It worked like a charm, and I was very happy about it.

In preparing to go the track today, I fired it up last night to warm it up. I heard a sound coming from the top end that sounded very much like a gear jamming in a car with a standard transmission. However the sound was very quick and fleeting and it went away and I didn't hear it again.

At the track today I noticed the sound again - right after start up when warming it up. Since it happened so similarly to the night before I just assumed that it had something to do with being a little cold.

However I started to worry a little more when out on the course I heard it every now and again. I had already planned on taking the bike into the shop to get a stripped bolt replaced, so I figured I'd just take it easy the rest of the morning and then have them look at it.

It got more frequent, until finally while in the air the sound came quite suddenly and loud and the bike died. When I kick it in an attempt to start it there is still normal compression and it turns over the same as before, but it doesn't respond at all. It acts like the kill switch is engaged.

My theory is this - the sound I heard was the timing chain missing the teeth on the new cam and as a result it wasn't spinning right (the sound is also akin to the sound your crank makes when your chain falls off). The timing chain would get back on though, and the bike would resume. However it kept happening to the point where the timing became so off that the engine isn't receiving any air, so it can't fire at all.

Is it possible I didn't tighten the chain tensor right after installing that would cause this? Or did I misunderstand and install a cam that just won't work?

I took it to a dealer and would like to be armed with as much input as I can when they call. The guy there treated me badly and I could tell he is the type that thinks owners shouldn't mess with their bikes like I did (this is another story - but the short is I would have and should have left immediately and taken it elsewhere, but I didn't have the time), so when he calls I want to have as much info as I can to counter any condescending negative comments I suspect he'll have for me.

Thanks for any thoughts/input.

[chickenstrips]

Tear it apart. Next time don't keep running it.

[Fullbore4]

I would call the dealer asap and tell them not to work on it and then go get it and take it apart.......you might luck out and find an obvious, inexpensive fix.....it does sound like a problem with the chain tightener but who knows.

[Nathanael]

Well I'll call them about it. I did have something they needed to do that I couldn't do, but if you guys think it might be a bad install on the cam and that I can fix it I wouldn't mind saving the money.

Just to clarify for anyone that has experience with the stuff I'm dealing with. I have a 2002 WR426 and I swapped out the stock exhaust cam for the OEM 03 YZ exhaust cam. I was told on this board that that was the one I would need. Did I install the right cam?

[R_Little]

Well I'll call them about it. I did have something they needed to do that I couldn't do, but if you guys think it might be a bad install on the cam and that I can fix it I wouldn't mind saving the money.

Just to clarify for anyone that has experience with the stuff I'm dealing with. I have a 2002 WR426 and I swapped out the stock exhaust cam for the OEM 03 YZ exhaust cam. I was told on this board that that was the one I would need. Did I install the right cam?

Yes it is the right one. Did you reset the came tensioner when you put the new cam in?

[Maddeh]

I'm the one who helped him install the '03 OEM cam. It seemed like the teeth were way off, but everything said that the pitch was different but it still worked.

When you say reset the tensioner, I would say no. All we did was take out the tensioner, change the cam, and put the tensioner back in. What do we need to do to reset the tensioner?

[matt4x4]

You need to take the bolt off teh outside, screw in hte screw inside that, it'll lock into place, mount the tensioner, give the screw a light twist and it'll pop the tensioner loose so it can tension the chain - I don't know HOW you would have gotten the tensioner in there any other way......

[Nathanael]

hrmm that sounds much more involved than how I did it. I simply held it in place, tightened the two bolts on either side, and then put the top bolt back in and tightened.

[matt4x4]

Well, if everything is installed right, and you put the chain tensioner in the hole JUST AS YOU PULLED IT OUT, it shouldn't even go in all the way because it unwound itself to it's maximum when you took it out, meaning, the pusher is out really far now. When you put it in, the two bolt holes shouldn't even meet the Cylinder, if you cranked the bolts in to get it in there, then likely you overstressed something or completely stretched your timing chain, Hercules.

BTW - Did you replace your timing chain when you did the cam??

If you actually turned it in using a small flathead, you would know because you have to do that when it's off the motor because you need to push the tensioner into the body as you turn the small flathead until it locks.

The third bolt is only a protective cover for the small flathead tensioner screw under it.

I don't understand how your bike could have done this (skipped teeth on cam) a number of times now without busting valves unless it's acted up when the valves were in their closed position and somehow lined itself back up again to be times properly........

[Nathanael]

Well, if everything is installed right, and you put the chain tensioner in the hole JUST AS YOU PULLED IT OUT, it shouldn't even go in all the way because it unwound itself to it's maximum when you took it out, meaning, the pusher is out really far now. When you put it in, the two bolt holes shouldn't even meet the Cylinder, if you cranked the bolts in to get it in there, then likely you overstressed something or completely stretched your timing chain, Hercules.

Yeah that's what I did. Crap. The hercules part made me laugh though. ?

BTW - Did you replace your timing chain when you did the cam??

No I didn't, and I'm gathering now that I will probably have to for sure.

If you actually turned it in using a small flathead, you would know because you have to do that when it's off the motor because you need to push the tensioner into the body as you turn the small flathead until it locks.

The third bolt is only a protective cover for the small flathead tensioner screw under it.

I don't understand how your bike could have done this (skipped teeth on cam) a number of times now without busting valves unless it's acted up when the valves were in their closed position and somehow lined itself back up again to be times properly........

I'm impressed that it worked then for the time I used it after the install. Judging by this I really screwed up. Hope I didn't break anything permanently.

[matt4x4]

Only thing I can see that MIGHT have put you in the situation you're in is:

Your timing chain was SO stretched that your Tensioner WAS ALREADY at it's max (when you unbolted it, did it want to push away from the cylinder or just sit there flush until you pulled it off?), if it was already at it's max, I can see it going back in without a problem or overtensioning your Timing chain - however, you also won't get proper tension on the chain, and the chain can then skip on the gears - usually, that ends up in busted valves (well, busted motor, not just valves).

I'd be taking the lid off, then the head, inspect the valves/piston because you may have done some bending on them, remove the chain and replace it - before you replace it, check it against the new one for difference in length.

AND DONT forget to turn your tensioner back in before install, THEN release it.

(run through how it works OFF the motor - you'll understand).

[Nathanael]

When I pulled it off it pushed away from the block. So does that mean it was tightened all the way or no? It was difficult to get back in, but I didn't have to push super hard either. I just seated in and then would turn each of the mount bolts separate, a turn at a time.

I'm obviously new to this kind of work, but from my work on the top end already it seems that replacing that chain would be a super hard deal. Wouldn't I have to remove most of the box to get at it properly? (is that what you called the head?)

[Strattos]

I don't understand how your bike could have done this (skipped teeth on cam) a number of times now without busting valves unless it's acted up when the valves were in their closed position and somehow lined itself back up again to be times properly........

Definitely make sure your tensioner is on properly. As mentioned above, you may have been VERY lucky, if this was the problem, not to have done a lot more damage.

I recently totalled my motor after dropping three inlet valves, which we think was traced back to some fault with the tensioner. Wrecked my head, inlet valves (obviously), piston and pot. Parts bill alone was more than $3000 here in Oz.

[matt4x4]

When you removed the tensioner, it started to unwind itself as you released it so it pushed away from the cylinder.

When you put it back in you essentially overtightened your cam chain by forcing a fully extended tensioner onto the chain.

At the very least, you WILL need a cam chain, possibly, no definitely (Don't take a chance), the tensioner, a headgasket because you are going to have to take your head off to inspect the cylinder/piston/valves and head surface for damage.

You will need to remove your flywheel and stator to get the bottom of the chain off.

If you were able to change a cam out, this isn't any harder, and while you have it open, might not be a bad idea to do a piston and rings - in which case you also need a base gasket.

Be careful taking off the stator cover and you can reuse the gasket.

Usually - if a valve hits the piston, you also have to do the bottom end sine the force of impact gets transfered through the entire motor assy.

[Maddeh]

I picked the bike up from the dealer this morning. Will be tearing into it tonight or tomorrow, we'll see what it looks like.

[Fullbore4]

The fact that you can turn it over with no ill sounds like valves hitting the piston or chain rubbing is a very good thing. I hope you come out okay. Keep us posted.

[matt4x4]

Still - pull it apart - if something did go wrong - you want to catch it BEFORE zipping it all up again.

As to your question regarding having to tear it all apart to do the chain - no, you have to take the stator cover off, the flywheel, the magneto, remove both cams, remove one bolt that holds the rear chain guide in place - the front just lifts out, drop the chain down the slot while it's connected to a stiff wire, pull the new one in with same wire, hooked under the bottom gear, put cams in again, set TDC, align cams etc and make sure all torque values are strictly adhered to.

Pulling the cylinder off isn't a big deal and it's cheap insurance to make sure nothing is wrong inside your combustion chamber - gaskets are cheap, pistons and heads aren't

[Nathanael]

We should start soon, we'll keep you posted.

[Nathanael]

Ok I haven't had a chance to look yet, but my brother has gotten in there to dig around.

There appears to be no damage at all to any engine parts (*phew*).

The reason the bike won't start is due to not getting any spark. This is odd because I just replaced the spark plug like 2 weeks ago. =/

I'm going over there tonight with a new spark plug and we'll take off the chain/cams and reset the timing etc. Any tips?

[matt4x4]

replace the timing chain AND tensioner - esp. after what you did to it - I can pretty much guarantee you stretched the heck out of it and didn't do the tensioner any favors.

I would also check/set your valve clearance and install new head and base gaskets.

If your brother already took it apart to look at everything you don't need to remove the cams since he already did.

Tie a wire onto the chain

in case that's not so, stuff a rag into the chain slot so you don't lose anything, remove cap bolts (4 and 6) remove caps, tilt both cams down and in at the same time and take chain off, remove cams.

Take off stator cover, remove flywheel (need puller - cheap harmonic balancer puller will work), stator, bolt on back chain guide.

Pull out both chain guides, lower chain down with wire

undo the bolts under the cams that hold the head/cylinder down, also do the small ones between head and cylinder on the outside - at this point you can pull the cylinder off the piston and check for play in your wristpin and big end, maybe replace rings and or piston while it's open.

Place a new base gasket on, put cylinder back on - (if you did rings and or piston, hone cylinder first - can be done with scotchbrite pads), put headgasket on, put head on, tighten down criss cross pattern to proper torque.

Put wire on new chain, set over gear and pull up using wire, insert chain guides, put on rear guide bolt - torque, put stator/flywheel and cover back on, torque, set TDC - keeping tension on chain so it doesn't snag,, put in proper shims if needed - make sure you add a dab of moly grease to each.

replace buckets, replace cams reverse to how you took them out - might take a couple of tries to get them to the right timing because you kind of roll them in/up/sideways to get them under the chain.

snug up caps (caps have half circle alignment circlips that need to fit right) in criss cross patern, slowly and carefully do each bolt a bit more until you get them torqued just right - better to say just a tad under specified or you may get a loud noise from top end if over torqued - has happened to a few.

Reset the NEW tensioner, install it, release it (best to play with it once or twice off the bike to see how it works/releases) put plug bolt back in.

Turn engine over 20 times to make sure everything is good and TDC and cam timing marks line up right.

Put lid/gasket back on - connect hoses and whatever else you took off to get to everything.

No spark can mean a couple of things - test your coil and stator - search for how to do it - requires simple tools.

Also might be a bad connection at a connector somewhere in the harness or a bad ground at the coil where it bolts to the frame or it can be a bad kill switch.

good luck - post back on findings and what repairs you did.